The synthesis and assembly of enveloped viruses and the biological role of viral glycoproteins will be studied. Rous sarcoma virus and Sindbis virus will be employed. The oligosaccharides of the glycoproteins of Rous sarcoma virus will be characterized as to size, sugar composition and to the number of chains per polypeptide. How these oligosaccharides vary as a function of the host range of the virus and how they are affected structurally by the transformed state of the host cell will then be examined. The degree to which the structure of viral oligosaccharides is determined by the host cell and the degree to which it is determined by the virus will be studied. This will be examined by (1) comparison of the glycosylation of Sindbis virus, vesicular stomatitus virus and Rous sarcoma virus when they are all grown in a single type of cell and (2) comparison of the glycosylation of Sindbis virus by a number of different cell types. The biosynthesis of the Sindbis virus glycoproteins and the assembly of the Sindbis membrane and virion will be studied. The experimental approach will be to examine intermediates which accumulate (1) in cells infected with temperature-sensitive mutants at the non- permissive temperature (2) in cells which only allow slow virus growth and (3) in infected cells in the presence of glucosamine and 2- deoxyglucose. Finally, the sequence in which sugars are attached to major glycoprotein of the avian tumor virus B77 will be compared with the glycosylation sequence seen with Sindbis virus.